RFR: 8286058: AArch64: clarify uses of MacroAssembler::trampoline_call

[Evgeny Astigeevich]

`MacroAssembler::trampoline_call` is for generating calls of targets which are inside CodeCache and can have relocInfo types: `runtime_call_type`, `opt_virtual_call_type`, `static_call_type` or `virtual_call_type`.
This PR updates the description of the function and adds additional asserts.
Tested a fastdebug build:
- `gtest`: Passed
- `tier1`: Passed

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Commit messages:
 - 8286058: AArch64: clarify uses of MacroAssembler::trampoline_call

Changes: https://git.openjdk.java.net/jdk/pull/8564/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8564&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286058
  Stats: 31 lines in 2 files changed: 31 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8564.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8564/head:pull/8564

PR: https://git.openjdk.java.net/jdk/pull/8564